Epicuticular wax is a waxy coating which covers the outer surface of the plant cuticle in land plants. It may form a whitish film or bloom on leaves, fruits and other plant organs. Chemically, it consists of hydrophobic organic compounds, mainly straight-chain aliphatic hydrocarbons with or without a variety of substituted functional groups. The main functions of the epicuticular wax are to decrease surface wetting and moisture loss. Other functions include reflection of ultraviolet light, assisting in the formation of an ultra-hydrophobic and self-cleaning surface and acting as an anti-climb surface. Chemical composition Common constituents of epicuticular wax are predominantly straight-chain aliphatic hydrocarbons that may be saturated or unsaturated and contain a variety of functional groups. These waxes can be composed of a variety of compounds which differ between plant species. Paraffins occur in leaves of peas and cabbages. Leaves of carnauba palm and banana feature alkyl esters. The secondary alcohol 10-nonacosanol appears in most gymnosperms such as Ginkgo biloba and Sitka spruce as well as many of the Ranunculaceae, Papaveraceae and Rosaceae and some mosses. Other forms of secondary alcohols are found in Brassicaceae including Arabidopsis thaliana. Primary alcohols (most commonly octacosan-1-ol) occur in Eucalyptus, legumes, and most Poaceae grasses. Other grasses feature β-diketones, as do Eucalyptus, box Buxus and the Ericaceae. Young beech leaves, sugarcane culms and lemon fruit exhibit aldehydes. Triterpenes are the primary component in fruit waxes of apple, plum and grape. Cyclic constituents are often recorded in epicuticular waxes but are generally minor constituents. They may include phytosterols such as β-sitosterol and pentacyclic triterpenoids such as ursolic acid and oleanolic acid and their respective precursors, α-amyrin and β-amyrin. Farina Many species of the genus Primula and ferns such as Cheilanthes, Pityrogramma and Notholaena produce a mealy, whitish to pale yellow glandular secretion known as farina that is not an epicuticular wax, but consists largely of crystals of a different class of polyphenolic compounds known as flavonoids. Unlike epicuticular wax, farina is secreted by specialised glandular hairs, rather than by the cuticle of the entire epidermis. Physical properties Epicuticular waxes are mostly solids at ambient temperature, with melting points above about . They are soluble in organic solvents such as chloroform and hexane, making them accessible for chemical analysis, but in some species esterification of acids and alcohols into estolides or the polymerization of aldehydes may give rise to insoluble compounds. Solvent extracts of cuticle waxes